From e68fd017bad00c1cd2e85d2616881b67417c5fcd Mon Sep 17 00:00:00 2001
From: Sviatoslav Sydorenko <wk@sydorenko.org.ua>
Date: Thu, 8 Apr 2021 19:58:24 +0200
Subject: [PATCH] Implement `find_spec` in vendored module importers

This change makes the import warning emitted by Python 3.10 disappear
but implementing the hook that is supposed to replace the old import
mechanism.

Refs:
* https://bugs.python.org/issue42134
* https://bugs.python.org/issue43540
* https://github.com/pypa/setuptools/issues/2632#issuecomment-815701078

Fixes #2632
---
 pkg_resources/extern/__init__.py | 20 ++++++++++++++------
 setuptools/extern/__init__.py    | 20 ++++++++++++++------
 2 files changed, 28 insertions(+), 12 deletions(-)

diff --git a/pkg_resources/extern/__init__.py b/pkg_resources/extern/__init__.py
index 1fbb4fcc896..962802fdc19 100644
--- a/pkg_resources/extern/__init__.py
+++ b/pkg_resources/extern/__init__.py
@@ -20,17 +20,18 @@ def search_path(self):
         yield self.vendor_pkg + '.'
         yield ''
 
+    def _module_matches_namespace(self, fullname):
+        """Figure out if the target module is vendored."""
+        root, base, target = fullname.partition(self.root_name + '.')
+        return not root and any(map(target.startswith, self.vendored_names))
+
     def find_module(self, fullname, path=None):
         """
         Return self when fullname starts with root_name and the
         target module is one vendored through this importer.
         """
-        root, base, target = fullname.partition(self.root_name + '.')
-        if root:
-            return
-        if not any(map(target.startswith, self.vendored_names)):
-            return
-        return self
+        spec = self.find_spec(fullname, path)
+        return spec.loader if spec is not None else None
 
     def load_module(self, fullname):
         """
@@ -60,6 +61,13 @@ def create_module(self, spec):
     def exec_module(self, module):
         pass
 
+    def find_spec(self, fullname, path=None, target=None):
+        """Produce a registered namespace matching module spec."""
+        return (
+            importlib.machinery.ModuleSpec(fullname, self)
+            if self._module_matches_namespace(fullname) else None
+        )
+
     def install(self):
         """
         Install this importer into sys.meta_path if not already present.
diff --git a/setuptools/extern/__init__.py b/setuptools/extern/__init__.py
index 399701a044e..94b6ddd6134 100644
--- a/setuptools/extern/__init__.py
+++ b/setuptools/extern/__init__.py
@@ -20,17 +20,18 @@ def search_path(self):
         yield self.vendor_pkg + '.'
         yield ''
 
+    def _module_matches_namespace(self, fullname):
+        """Figure out if the target module is vendored."""
+        root, base, target = fullname.partition(self.root_name + '.')
+        return not root and any(map(target.startswith, self.vendored_names))
+
     def find_module(self, fullname, path=None):
         """
         Return self when fullname starts with root_name and the
         target module is one vendored through this importer.
         """
-        root, base, target = fullname.partition(self.root_name + '.')
-        if root:
-            return
-        if not any(map(target.startswith, self.vendored_names)):
-            return
-        return self
+        spec = self.find_spec(fullname, path)
+        return spec.loader if spec is not None else None
 
     def load_module(self, fullname):
         """
@@ -60,6 +61,13 @@ def create_module(self, spec):
     def exec_module(self, module):
         pass
 
+    def find_spec(self, fullname, path=None, target=None):
+        """Produce a registered namespace matching module spec."""
+        return (
+            importlib.machinery.ModuleSpec(fullname, self)
+            if self._module_matches_namespace(fullname) else None
+        )
+
     def install(self):
         """
         Install this importer into sys.meta_path if not already present.